@mixin back-to-top-sidebar {
  .back-to-top {
    display: none;
    margin: 15px -10px -20px;
    background: $body-bg-color;
    font-size: $b2t-font-size;
    opacity: $b2t-opacity;
    cursor: pointer;
    text-align: center;
    -webkit-transform: translateZ(0);
    transition-property: bottom;
    @include the-transition();
      &:hover { opacity: 0.8; }

    @include mobile() {
      display: none;
    }
    @include tablet() {
      display: none;
    }

    &.back-to-top-on {
      display: block;
    }
  }
}
